Get tooltips data from python?
Wow Blender/Python is really like an onion ( a rather large on at that ) and my eyes have been watering like made getting through the layers :)

Ok I finally ran grep in the scripts directory as I should have when pink vertex first sugessted it. Duh.
Line 340 in bl_extract_messages.py gives it up (code below). So it looks to me that if it doesn't have a bl_rna.description (or bl_description) then it uses the __doc__ part. 
In the process I realised that the bulk of what I need is directly in the keymaps them selves as .name attribute of the individual keymap. This is derived from the bl_label that is in the op that is called by the new keymap definition line.

So I went round in circles when it was right under my nose.
Thanks again everyone.

    if bl_rna.description:
        process_msg(msgs, default_context, bl_rna.description, msgsrc, reports, check_ctxt_rna_tip, settings)
    elif cls.__doc__:  # XXX Some classes (like KeyingSetInfo subclasses) have void description... :(
        process_msg(msgs, default_context, cls.__doc__, msgsrc, reports, check_ctxt_rna_tip, settings)